Hydrogen is a very attractive fuel because it is clean and can be used to efficiently produce electricity in a fuel cell. The automotive industry expends significant resources in the development of hydrogen fuel cells as a source of power for vehicles. Such vehicles would be more efficient and generate fewer emissions than today's vehicles employing internal combustion engines.
A hydrogen fuel cell is an electro-chemical device that includes an anode and a cathode with an electrolyte between the anode and the cathode. The anode receives hydrogen-rich gas or pure hydrogen and the cathode receives oxygen or air. The hydrogen gas is dissociated in the anode to generate free protons and electrons. The protons pass through the electrolyte to the cathode, where the protons react with the oxygen and the electrons in the cathode to generate water. The electrons from the anode are unable to pass through the electrolyte. Therefore, the electrons are directed through a load to perform work before they are sent to the cathode. The work may be used, for example, to operate a vehicle.
Several fuel cells are typically combined in a fuel cell stack to generate the desired power. The fuel cell stack includes a series of bipolar plates. For the automotive fuel cell stack mentioned above, the stack may include about two hundred or more bipolar plates. The fuel cell stack receives a cathode reactant gas, typically a flow of air forced through the stack by a compressor. Not all of the oxygen is consumed by the stack and some of the air is output as a cathode exhaust gas that may include liquid water as a stack by-product. The fuel cell stack also receives an anode hydrogen reactant gas that flows into the anode side of the stack.